Shaving apparatus



G. H. RoBERtsoN Filed March 15 ,A 195o FIG. n.

w n\ Q \M\ @M m N Q5 wm F INVENTOR GEORGE H. ROBERTSON Patented Nov. 18, 1952 UNITED STATES PATENT OFFICE SHAVING APPARATUS George H. Robertson, Bellerose, N. Y., assignor to The Roto-Shaver, Inc., New York, N. Y., a corporation of Connecticut Application March 15, 1950, Serial No. 149,783

(Cl. Sil-43) 9 Claims.

This invention relates to shaving apparatus, and has particular reference to shaving apparatus of the type in which a rotary cutter traverses the underside of a perforate shear plate about an axis disposed normal thereto.

Shaving apparatus of the general type described utilize a shear plate having a convex configuration giving the shear plate the self-sustaining property so as to enable it to withstand shaving pressure Without flexing and the capacity to restore itself to shape when flexed, while at the same time enabling the shear plate to have the thinness essential to provide a close shave. Because of its shape the convex shear plate has a limited eiective shaving area, as compared to a flat shear plate, but because of the inherent Weakness of a flat surface having the thinness necessary to a close shave, the iiat shear plate heretofore has been conned to the narrow shavers of the reciprocating type and even there it has been acknowledged that support against the flexing caused by the shaving pressure is necessary, as is indicated in Patent No. 1,721,530, for example.

In accordance with the present invention, a at shear plate shaving apparatus of the large area rotary type is provided, in which the inherent weakness of a flat shear plate of large area having the thinness necessary for close shaving is compensated for by supporting it against material flexing and restoring its fiat shape when flexed during use, so that the shaving advantages of a flat shear plate are obtained and maintained.

In a preferred embodiment of the invention, a at, thin, perforate shear plate is traversed on its under surface by two or more blades rotated about an axis substantially normal to the shear plate and so constructed and arranged as to exert a continuous counter-pressure against the underside of the shear plate on the order of the pressure with which the shear plate is pressed against the skin during the shaving operation. This counter-pressure of the blades against the shear plate is derived from the centrifugal force of rotation of the cutter member carrying the blades and is provided at the proper magnitude by,

mounting and arranging the center of .gravity of rotating parts so as to produce that force in.,

the right direction.

It will be seen that the shaving apparatus of this inventionrealizes in a practical and effective way the desirable large area shaving surface provided by a flat shear plate of the desired thinness. v, I

Fora more complete understanding, 'reference may be had to the accompanying drawings, in which:

Figure 1 is a plan View of the shaving apparatus of the invention, with the center part of the shear plate shown broken away to illustrate the construction of the centrifugal blade holders;

Fig. 2 is a section taken in a plane parallel and adjacent to the axis of rotation of the blade holder, as seen along the line 2-2 of Fig. 1;` and Fig. 3 is an enlarged transverse section through the blade holder and blade, as seen along the line 3-3 of Fig. 2.

Referring to the drawings, numeral l0 generally designates a frame or handle of any dethin flange of the collar 2l, as indicated at 23.

in Fig. 2. The shear plate 22 has the general characteristics of the shear plate described-in said Patent No. 2,280,836 in that it is thin, on ,the order of a few thousandths of an inch, so as to afford a close shave, and is pierced with closely-spaced perforations on the order of .025 inch in diameter, but instead of being convex, the shear plate 22 is flat or plane, as shown especially in Fig. 2. Because of its extreme thinness, the fiat shear plate 22 has no inherent shaperetaining or restoring property and, when applied to the skin with normal shaving pressure on` the order of three-quarters of a pound per square inch, it will flex and is not inherently capable of rapidly recovering its flat shape without aid. 1 f

Secured to the projecting end of motor shaft Il by means of a set screw 24 or equivalent fastening means. is the blade support or rotor of the shaver which includes the center stem 25 having a socket for the reception of the motor` 3 No. 2,280,836 as affording the said support for the center of the shear plate 22.

The opposite sides of the stem 26 are flattened and the stem 26 is fitted with a pin 28 extending therethrough and serving as a pivot for a pair of oppositely-extending blade holders 29 and 30, as best shown in Fig. l.

Each blade holder 29, 33, preferably is formed of a sheet metal stamping comprising a channelshaped body portion 3|, best shown in Fig. 3, having parallel lugs 32 and 33 at one edge by means of which the corresponding holder is pivoted on pin 28. 'I'he lugs 32 and 33 are positioned opposite the upper `edge of the corresponding holder, and lug 32 is oiset laterally from the lug 33, and the latter is an extension of the trailing edge of the channel ,3| as shown in Fig. 1. Accordingly, as the 'blade-holding arms 29 and 39 are rotated in the direction -of the arrow in Fig. l, the lug 32 leads, and the lug 33 `followsan axial plane parallel to each. Also, the leading flange of -the blade holder channel 3| Vto which lug v32 is connected, lies approximately in the said axial plane. Accordinglythe blade holders 429 ,and 33 hold the corresponding blades 435 in such a positibn 'as to give 4the raking cut described in said Patent No. 2,280,836, with its 'attendant advantages.

Referring to 'the sectional viewof the 'channel 3] of ea'ch of 'therblade holders 29 and 30, it will be observed inFig. v3fthat the 'channel is V-shaped'and the blade 35 tilts in Aafdirecti'on opposite to the direction of `its movement within the limits of the 'channel v31|"so as to continuously present the sharp edge to the hairs 'projecting 'through the perforations 'in the shear Vplate when 'the blade 35 traverses the underside thereof inthe position shown Vin Fig. 3. Also, the blade 35 vis 'self-honing, 'as w'ill be readily understood. This lean back blade feature of construction and operation form no 'partof the present invention, being Vdisclosed by saidPatent No. 2,280,836.

Instead vof resting lon the bottom of the channel\'3"|, ythe blade '35 rests on r'a pin 36 extending across 'the blade lslot 3j'| of the channe'l'3l so that ther lower edge Vof lthe blade is 'spaced slightly above the bottom of the channel, asfshown in Fig. 12; 'The' hole '38 in the blade 35 .is oversized; so that 'the 'blade free to tilt backwardly in response to the Trictional Adrag `against the underside of hthe vshear plate y32, s o that Iit may assume Ythe position vshownl in Fig. @3.

When the 4shaver is not in operation, the blade holders 29 and 39 drop downwardly by'lgravity about their pivot pin 28 until the lheel 39 ofthe corresponding blade holder rests against the spacing-bead Y40 on thestem 25,so that lthe -blade 35 is 4disengaged from the underside of the shear out its length with the shear plate 22 without,

plate, as Yis .indicated by the Vdotted lines in Fig.

2. When the shaver is placed into operation, the low center of gravity of each. blade holder 29, i39, being located ata point G approximately directly below the center of the pivot pin 33 for the corresponding blades 3,5, the centrifugalforce of rotation causes the `center of gravity G to tend to move upwardly into alignment with the axis of'pivotpi'n '28. The movement of the blade holders 29 and 30 in this upward direction about pin za 'is rimmed by the shear 'plate 2,2 against which blade 35 is stopped, so that blade Y35 traverses the -underside of the shear plate in the direction shown :by the arrows in Figs. 1 and 3 t'o-shear-hairs projecting vthrough the perforations 'of the shear plate 22.

By reason of the eccentric position of the center of gravity :G of each of the 'blade vrualderls 4 29 and 30 below the plane of the pivot pin 28 and displaced laterally therefrom, the blades 35 are pressed against the underside of the shear plate 22 with a considerable pressure, at least on the order of the pressure with which the shear plate 22 is normally placed against the skin, namely, on the order of three-quarters of a pound per square inch. Preferably, the counter-pressure of the blades 35 due to the eccentric position of the centers of gravity G of the blade holders 29 and 33 is somewhat greater than the normal shaving pressure to imediately compensate for any exceptional pressures which might cause the shear plate `to be distorted momentarily. However, the counter-pressure of the blades should not be so great as to create a disproportionately high drag load on the motor er to create frictional heat. These conditions can be made by selection of the proper weights and lever arms for the blade holders 29 and 30.

Theslight spacing of 'the bottom edge of the blade 35 above the bottom of the channel 3| permits blade 35 to tilt laterally t'o a limited degree about the axis provided by the pivot pin 36 so that the blade 35 accommodates the relative angular disposition of the blade holders 23 and 30 so as to be always in linear contact throughhowever, being free to tilt sufficiently to tear 'the shear plate in response to a temporary deformity of the shear plate under shaving pressure. By positioning the pivot pin 36 for each 'blade 35 approximately in axial line with the center of gravity G, the blade is balanced and may pivot and the blade holders 29 and 30 do not swingV upwardly to press the corresponding blades 35 against the shear plate 32 until a predetermined speed is attained, and thereafter, the pressure increases to that provided by maximum speed of rotation of the blade holders.

This pressure does not exceed the predetermined I point, and immediately decreases as the motor is shut off inasmuch as the blade holders 2 9 and 30 drop away from the shear plate to the point where their heels 39 engage the bead 43. By adjusting the weights of the blade holders 2'9 and 30 and the lever arm from the center of roe tation to the center of gravity G or the speed of the motor, the pressure of the blades lagainst the underside of the shear plate may be varied 4 to suit requirements. For example, if a vconvex shear plate of extraordinary thinness is desired, part 0f its strength may be obtained by its convex shape as in said Patent No. 2,280,836, and may be augmented by the pressure `of the blades against its underside in accordance with the present invention. The same effect wouldV be obtained were 'a wide vangle Aconical Yshear plate desired instead vof the nat shear plate.

A simple way to adjust 'the Weight of Vthe-bladev holders is to substitute pins 36 with di-ierent Weights, such as pins having dileren'tsized heads In order to provide for ready expulsion of the cut hairs dropping into the 'blade holding channels 31, the channels 3| are pierced along their bottom edges by slots 4|, through which the hair may ran, aided by air-sowing through-holes t2- in-,the leading face of the channels 29 and .3.0 ,asv

shown'fin Figs. 1 and 3.. Also, the centrifugal force expels hair outwardly through channels 3 l, whose ends 43 are tapered downwardly ,to permit freedomv of centrifugal hair expulsion and also to reduce tip windage, although the holders 29 and 30 may be made any desired shape to suit requirements. The hair collects in the space between head 20 and the casing l0 and may begremoved by disengaging the former from the latter.

Operation of the new shaving apparatus of lthis invention will be readily understood from the foregoing description of the parts of which' itis composedand their functions. It .affords a fiat shear plate shaving device with all its advantages, but without the disadvantages of instability under shaving pressure, which the counter-pressure provided by the blades having the effect of lending to a very thin shear plate a stiffness otherwise obtained only by making the shear plate too thick to provide the desired close shave. The counter-pressure is applied only during shaving, and hence, does not impose a continuous static,v load on the motor.

Although a preferred embodiment of the invention has been illustrated and described herein, it is to be understood that the invention is not limited thereby, but is susceptible of changes in form and detail within the scope of the appended claims.

I claim:

1. In shaving apparatus, the combination of a thin perforate shear plate adapted to engage the skin, a, drive shaft rotating about an axis substantially normal to said shear plate, a pivot on said shaft extending substantially normal to said axis and positioned adjacent said shear plate, a blade holder mounted on said pivot and having its center of gravity spaced a substantial distance from said shear plate, and a blade mounted on said blade holder and adapted to be moved into wiping engagement with said shear plate by the blade holder in response to centrifugal force upon rotation of said shaft.

2. In shaving apparatus, the combination of a thin perforate shear plate adapted to engage the skin, a drive shaft rotating about an axis substantially normal to said shear plate, a, pivot on said shaft extending substantially normal to said axis and positioned adjacent said shear plate, a channel-shaped blade holder mounted on said pivot and having its center of gravity spaced a substantial distance from said shear plate, and a blade mounted in the channel of said blade holder and adapted to be moved into wiping engagement with said shear plate by the blade holder in response to centrifugal force upon rotation of said shaft.

3. In shaving apparatus, the combination of a thin perforate shear plate adapted to engage the skin, a drive shaft rotating about an axis substantially normal to said shear plate, a pivot on said shaft extending substantially normal to said axis and positioned adjacent said shear plate, a blade holder mounted on said pivot and having its center of gravity spaced a substantial distance from said shear plate, stop means normally holding said blade holder close to said shear plate when the shaft is at rest, and a blade mounted on said blade holder and adapted to be moved into wiping engagement with said shear plate by the blade holder in response to centrifugal force upon rotation of said shaft.

4. In shaving apparatus, the combination of a thin perforate shear plate adapted to engage the 6.. skin, a drive shaftrotatlng about an axis substantially normal to said shear plate, Ya pivot on said shaft extending substantially normal to said axis and positioned adjacent saidshear plate,

a blade holder mounted on said -pivot and hav-A ing its center of gravity spaced a substantial distance from said shear plate, and a blade pivoted about 'an-.axis substantially parallel .tosaid pivot an'dj lying in a plane parallelto said axis and including the said center of gravity of said blade holder and adapted to be moved into wiping engagement .with said shear plate by the blade holder in response to centrifugal force upon rotation of said shaft.

5. In shaving apparatus, the combination of a thin perforate shear plate having a surface of revolution adapted -to engage the skin, a drive shaft rotating about an axis including the center of revolution of said shear plate, a pivot on said shaft extending substantially normal to and including said axis and positioned adjacent said shear plate, a blade holder mounted on said pivot and having its center of gravity spaced a substantial distance from said shear plate, and a blade mounted on said blade holder and adapted to be moved into wiping engagement with said shear plate by the blade holder in response to centrifugal force upon rotation of said shaft.

6. In shaving apparatus, the combination of a thin, at, perforate shear plate adapted'to engage the skin, a drive shaft rotating 'about an axis substantially normal to Said shear plate, a pivot on said shaft extending substantially normal to said axis and positioned adjacent said shear plate, a blade holder of substantial mass mounted on said pivot and having its center of gravity spaced a substantial distance from said shear plate, and a blade mounted on said blade holder, whereby the blade holder urges said blade into engagement with said shear plate in response to centrifugal force with sufllcient force to substantially counteract the shear plate deilecting pressure of the latter against the skin in use.

'7. In shaving apparatus, the combination of a thin, fiat, perforate shear plate adapted to engage the skin, a drive shaft rotating about an axis substantially normal to said shear plate, a pivot on said shaft extending substantially normal to said axis and positioned adjacent said shear plate, a plurality of blade holders of substantial mass mounted on said pivot and each having its center of gravity spaced a substantial distance from said shear plate, and a blade mounted on said blade holder, whereby the blade holder urges each blade into engagement with said shear plate in response to centrifugal force with suillcient force to substantially counteract the shear plate deilecting pressure of the latter against the skin in use.

8. In shaving apparatus, the combination of a thin perforate shear plate adapted to engage the skin, a drive shaft rotating about an axis substantially normal to said shear plate, a. pivot on said shaft extending substantially normal to said axis and positioned adjacent said shear plate, a blade holder mounted on said pivot and having its center of gravity spaced a substantial distance from said shear plate, a pinon said blade holder and having substantial weight for augmenting the effect of centrifugal force on said blade holder, and a blade pivoted on said pin and adapted to be moved into wiping engagement with said shear plate by the blade holder in reV 

